I recently purchased an early model 2015 Leisure Travel Van, Unity MB model that did not have the solar option. This turned out to be a plus as I was able to over double the factory wattage and hopefully wire it more efficiently. Although new at this, I had tremendous help and mentoring from "Klipstr" on the Sprinter UnityForum and thought I might share the installation and what I learned in the process.

Disclaimer: I'm new at this. Use the information at your own risk. I researched what I could find and asked questions. Hopefully this will be another helpful resource for others wanting to do it themselves.

The "factory solar pre-wire" consisted of a pair of 8AWG wires and a single 12AWG wire running for the control cabinet​ above the entry door ​directly to the battery box. The issue with the factory pre-wiring was the wires sizes were too small and didn't allow for the proper installation of a charge controller close enough to the battery box to prevent voltage loss without installing heaver wire.

With the help of Kelly Lipp​, I decided to start over. I was able to install 4 Suaoki 100W 18V 12V Solar Panels on my Unity. I would have preferred to have installed ​5 panels but due to a previous installation of a satellite TV cable, I only had room for 4 panels without re-routing the satellite cable to another location. Important: Cut out rectangles of cardboard from the solar panel shipping boxes and temporarily tape them to the solar cells to prevent electrical shock when doing the installation. Leave enough room around the edges of the panels and the RV roof to clean with acetone prior to applying the eternabond tape. Attach your panels as far away as you can from other roof items to prevent shadows on the panels. Even a very small shadow on just a small part of the panel will drastically reduce to current output.

I attached the panels, combiner box, and secured the wires with Eternabond 2" tape. I've used Eternabond on my previous class A with great success to seal seams. Once it sticks, it's there for good. It made it a good looking, streamline installation too. (Important: Before ordering any flexible panels, make sure they haven't been subject to a recall.)

I ran all my ​solar panel wires to a combiner box (buss bars purchased at Lowe's) that was attached with eternabond tape to eliminate extra holes thru my roof. I needed to extend some of my solar panel cables to the combiner box. You can make your own cables with extra MC4 panel connectors and a crimping tool, however, it was easier for me to purchase a pair of 8AWG, 10' & 3' pre-made cables with connectors and cut them to the correct length to reach the combiner box utilizing the attached connector. Never used my extra connectors or crimpers.

I ran a pair of 6AWG wires from the combiner box thru a 2-wire gland into the top of the tall closet to the left of the entry door (looking from the inside out). I attached it with 6 self-tapping screws and ​sealed it with Dicor self-leveling sealant.

I installed a 30 amp breaker on the positive, 6AWG wire running to the Bogart Engineering SC-2030 Solar Charger. Important: Leave the breaker open until everything else is connected (pic shows closed)! I would have used a 40 amp breaker if I had been able to use (5) 100W panels. A 30 amp breaker was adequate for my installation.

The two 6AWG wires continued downward to connect to the Bogart Engineering SC-2030 Solar Charger which was installed about 15" above the floor (close to the battery box). Note: I should have installed the Solar Charger vertically to allow the fins to provide better cooling.

After you have installed the Solar Charger, it will be necessary to drill a hole(s) thru the floor then another hole(s) into the side of the battery box to run the pair of 4AWG welding wires to the battery box. I also ran a 4-wire harness from the Tri-Metric TM-2030 Battery Monitor in the control cabinet above the entry door to the battery box at the same time. It's a good idea to install a battery box temperature sensor from the battery box to the SC-2030 Charge Controller at the same time. I mounted the sensor on the inside wall of the battery box compartment. You will also need to drill a hole in the base of the SC-2030 Charge Controller to fit a 4-wire phone cable (goes up to the TM-2030 Battery Monitor in the control cabinet) and the battery temp sensor wire that runs to the battery box.

I installed another 30 amp breaker on ​the positive 4AWG wire ​from the Charge Controller ​to the positive terminal of the battery bank.​ Leave the 30 amp breaker open for now. (pic shows open). Important: Remove the 1 amp fast acting fuse from the B1 (red) wire of the 4-wire harness until all wiring from the Charge Controller to the battery and from the Charge Controller to the Battery Monitor is complete. Attach this 1 amp fused wire to the positive terminal of the battery bank. Install a 500 amp shunt (recommended size) between the batteries on the battery box wall.

Attach a short 2/0AWG battery cable to one of the large bolts on one side of the shunt and the other end of the cable to the negative terminal of your battery bank. Important: There should not be any other wires connected the large bolt on that side of the shunt or to the negative terminal of the battery. Connect all other negative cables (cables to ground, negative 4AWG cable from the Solar Controller, etc.) to the other large bolt on the shunt.

Attach the G1 & G2 wires (2 black wires) from the 4-wire harness to the small Klevin screw on the "load side" of the shunt. The "SIG" wire (white wire) attaches to the Klevin on the "battery side" of the shunt as shown:

It's not difficult to access the backside of the control cabinet. There are 5 screws to remove the access door. There are 3 screws across the top and a few more at the bottom of the panel to remove it. Most of the electrical connections between the coach and the panel are quick disconnects. I had to clip 2 wires that ran to my water heater temperature controller (on-demand water heater). Other than that, a piece of cake.

I cut the hole for the Solar Monitor with a fine blade jigsaw. It was a little messy as the plastic re-welded itself to the cut but worked ok. Sure there is a better way.

Connect the 4-wire phone cable from the Charge Controller to the phone cable jack on the Battery Monitor. Attach the wiring harness wires from the battery box ​to lugs G1, G2, SIG & B1 on the Battery Monitor. Also, if you choose to monitor a 2nd battery (chassis battery), connect the extra wire from the chassis battery to lug B-2.

Cross your fingers! Remove the cardboard covers on the panels. Install the 1 amp fuse in the wiring harness at this time. The Battery Monitor should light up. Close both 30 amp breakers on the positive wire from the solar panels. It should work great. Mine did.

And here is a link to my blog where Jim kindly allowed me to post his work. Perhaps a bit easier to look at as you don't have to click the photos to see them... Not all of his words are there but you can get the gist.
Thanks to Jim for allowing me to post his work...

I set P-3 to 200 after some information I gleaned from HandyBob. He suggested the P-3 capacity setting be reduced by at least 10% from the factory claim of capacity to be more accurate. Ten percent less of 232 would be 208.8 however you must select settings in multiples of 10 so set it at 200. Could have set it at 210 also.

Without trivializing the amount of work that lvuman did on his rig it should be noted that he went from not being sure how to do this to doing it in the period of about two weeks! My point is most of you can probably do this on your own! If you need help, ask here or contact me. I am happy to get you started. I'm trying to find a good alternative to the flex panels that will fit on the roof. AMSOLAR has 100W aluminum framed panels that look good but require a bit more installation than simply gluing down the flat panels. The install looks good but one would be drilling at least eight holes per panel to mount them. Or glue the mounts down...

Bottom line: solar on Unity is evolving because of all the work being done here! Jump on!

AMSOLAR has 100W aluminum framed panels that look good but require a bit more installation than simply gluing down the flat panels. The install looks good but one would be drilling at least eight holes per panel to mount them. Or glue the mounts down...

Drilling holes is definitely not required. AM Solar recommends using the 3M VHB tape strips to attach their mounts. It's easy and takes about 5 minutes per panel.

You could also use something like Weld-Mount studs if you don't trust the VHB. But we've put about 1,300 miles on the van since installing the panels and had no problems (and AM Solar says they have not had any reports of separation AFAIK).